1. Field of the Invention
The present invention relates to power management and cooling in a computer system, such as in a rack-mounted computer chassis.
2. Description of the Related Art
The cost to both power and cool a computer system are important considerations in the design, development, and operation of computer systems. Computer systems generate heat as a result of consuming electrical power, and typically require a cooling system to maintain acceptable internal operating temperatures. For example, in a rack-mountable computer system, fans are typically included, either in the rack-mounted components to be cooled or as part of a rack-mounted fan assembly, for generating airflow through the computer system. The airflow rate may be dynamically varied according to the cooling needs, which vary over time. The cooling needs may vary, for example, according to the load placed on electronic components and the corresponding power consumed by the electronic components. Cooling fans consume power in addition to the power consumed by the components that are cooled by the cooling fans. Thus, the power consumption of cooling fans must be factored into the total amount of power available to the computer system.
The power consumed by fans may dramatically increase as a function of fan speed. For example, the power consumption of a fan may be a cubic function of fan speed, such that doubling the speed of a fan can lead to an eight-fold increase in the power consumption of the fan. Additionally, due to various regulations promulgated by industry standards-setting organizations, computer systems are designed for continuous operation under the maximum load that the computer systems are capable of handling in service. Thus, for example, a computer system may be configured to operate the fans at maximum speeds under extreme ambient temperature conditions, in which case the fans may consume a large amount of power. Other equipment such as power supplies and power cables may also be specified according to worst-case conditions, which increases the cost of the computer system.